Laser-assisted In Situ Keratomileusis Eyes Research Articles

Comparison of Subjective Visual Experiences and Ocular Symptoms After Wavefront-Guided and Wavefront-Optimized LASIK in a Prospective Fellow Eye Study

The purpose of this study was to compare the subjective visual experience and ocular symptoms of fellow eyes treated with wavefront-optimized (WFO-) laser-assisted in situ keratomileusis (LASIK) and wavefront-guided (WFG-) LASIK. Prospective randomized fellow eye, controlled study. Two hundred eyes of 100 subjects from a single academic center were enrolled and randomly assigned to treatment with WFO-LASIK in one eye and WFG-LASIK in the fellow eye. Subjects filled out a validated 14-part questionnaire for each eye at the preoperative visit and at postoperative months 1,3,6,12. In comparing the number of subjects who reported symptoms in the WFG- vs WFO- LASIK eyes, there was no difference in number reporting any visual experience (glare, halos, starbursts, hazy vision, blurred vision, distortion, double or multiple images, fluctuations in vision, focusing difficulties, and depth perception; all p>0.05) or ocular symptoms (photosensitivity, dry eye, foreign body sensation, ocular pain; all p>0.05). There was no preference for WFG-LASIK (28%) or the WFO-LASIK treated eye (29%) with most subjects reporting no preference (43%; Chi-squared p=0.972). Of the subjects who preferred one eye or the other, the preferred eye saw statistically better than the fellow eye (0.8 ± 1.4 Snellen line, p=0.0002). There was no other difference in subjective visual experience, ocular symptoms, refractive characteristics when taking into account eye preference. Most subjects had no eye preference; and for subjects who did have eye preference, the only detectable difference was better visual acuity in the preferred eye.

Status of Residual Refractive Error, Ocular Aberrations, and Accommodation After Myopic LASIK, SMILE, and TransPRK.

To analyze residual refractive error, ocular aberrations, and visual acuity (VA) during accommodation simultaneously with ocular aberrometry in eyes after laser-assisted in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), and transepithelial photorefractive keratectomy (TransPRK). Ocular aberrometry (Tracey Technologies, Houston, TX) was performed 3 months after LASIK (n = 95), SMILE (n = 73), and TransPRK (n = 35). While measuring the aberrations, VA was measured at distance (20 ft), intermediate (60 cm), and near (40 cm) targets. The examinations were done monocularly. A parallel group of age-matched normal eyes (n = 50) with 20/20 Snellen distance VA also underwent aberrometry. Distribution of residual spherical error of LASIK eyes matched the normal eyes the best, followed by SMILE and TransPRK. However, the distribution of cylindrical error of the SMILE eyes was distinctly different from the rest (P < .05). The SMILE eyes tended to be undercorrected by approximately 0.25 diopters (D) on average at all reading targets compared to LASIK eyes (P < .05). The undercorrection was greater when the magnitude of the preoperative cylinder exceeded 0.75 D (P < .05). The VA of LASIK and SMILE eyes was similar to normal eyes at all targets, but the TransPRK eyes were marginally inferior (P < .05). Only the ocular defocus changed differentially between the study groups during accommodation and the magnitude of change was least for TransPRK eyes (P < .05). However, postoperative near and intermediate accommodation of LASIK eyes were similar to normal eyes, followed by SMILE eyes and then TransPRK eyes. The refractive and aberrometric status of the LASIK eyes was closest to the normal eyes. The SMILE procedure may benefit from slight overcorrection of the preoperative refractive cylinder. [J Refract Surg. 2019;35(10):624-631.].

In Vivo Prediction of Air-Puff Induced Corneal Deformation Using LASIK, SMILE, and PRK Finite Element Simulations.

To simulate deformation amplitude after laser-assisted in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), and photorefractive keratectomy (PRK) with finite element models. Finite element simulations of air-puff applanation on LASIK, SMILE, and PRK models were performed on a cohort of normal eyes, which had undergone refractive treatments. Short- and long-term wound healing responses were considered for SMILE and LASIK models based on evidence of microdistortions in Bowman's layer and crimping of collagen fibers. First, inverse simulations were performed to derive the preoperative properties of the cornea. Using these properties and planned refractive treatment, postoperative air-puff deformation amplitude was predicted and compared with the in vivo measurements. The predicted postoperative corneal stiffness parameters agreed very well with in vivo values of SMILE, LASIK, and PRK eyes. Intraclass correlations (ICC) were greatest in PRK eyes (ICC > 0.95). This agreement was lower for peak deformation amplitude and peak deflection amplitude in SMILE and LASIK eyes (ICC < 0.9). In PRK eyes, peak deformation and deflection amplitude predictions were the best relative to in vivo magnitudes. Also, linear correlation (r) between in vivo measurement and predicted biomechanical parameters indicated strong agreement between them (SMILE: r ≥ 0.89, LASIK: r ≥ 0.83, PRK: r ≥ 0.87). The is the first study to present predictive simulations of corneal deformation changes after different procedures. Patient-specific preoperative corneal biomechanical properties and finite element models were a significant determinant of accurate postoperative deformation amplitude prediction.

Impact of hypoxic and mesopic environments on visual acuity, contrast sensitivity and accommodation in subjects with LASIK surgery and aircrew candidate

BackgroundThe safety of Laser-assisted in situ keratomileusis (LASIK) in aircrew was unclear, in addition, LASIK was not yet approved for aircrew of Taiwan Air Force. This study was aimed to evaluate visual performance in LASIK eyes in hypoxic and twilight environment. Methods48 myopic eyes of 24 subjects enrolled in this study were divided into LASIK group and control group. Subjects were exposed in hypoxic (15% O2) and mesopic (3 cd/m2) environment. Visual performance was evaluated using the Early Treatment of Diabetic Retinopathy Study (ETDRS) visual chart, and Functional Acuity Contrast Test (FACT) before and after the expirement. Physiological parameters of all subjects were measured and recorded throughout the experiment. ResultsThere was no significant difference of the two groups regarding their age, height, weight, and BMI. There is significant difference of preoperative spherical refractive error between the two groups. The results of physiological parameters were similar between two groups. Under normoxic conditions, there were no significant difference regarding distant vision in photopic and mesopic environments, so as for near vision. As a whole, the contrast sensitivity of the LASIK group were lowered than that of the control group about 35%, under whether normoxic or hypoxic conditions; photopic or mesopic circumstances. Under normoxic conditions, the measured accommodation of the LASIK group were 21% lowered than that of the control group and 31% lowered under hypoxic circumstances. ConclusionThere was no significant difference of visual acuity between the two groups regarding hypoxic and mesopic environment, but reduced contrast sensitivity was significant in LASIK group as compared to those of the control group. Accommodation was significantly lowered in LASIK group, compared with control group, in hypoxic environment. Whether postoperative visual performance after LASIK in aircrew during flying duty is safe might need further investigation.

A retrospective analysis of the postoperative use of loteprednol etabonate gel 0.5% following laser-assisted in situ keratomileusis or photorefractive keratectomy surgery.

BackgroundWhile loteprednol etabonate ophthalmic gel 0.5% (LE gel) is approved for treatment of postoperative ocular inflammation and pain, there have been no reported studies in patients undergoing laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK).MethodsThis was a retrospective chart review conducted at five refractive surgical centers in the USA. Data were collected from primary LASIK or PRK surgery cases in which LE gel was used postoperatively as the clinician’s routine standard of care and in which patients were followed-up for up to 6 months. Data extracted from charts included patient demographics, surgical details, LE gel dosing regimen, pre- and postsurgical refractive characteristics, intraocular pressure (IOP) measurements, and visual acuity. Primary outcomes included postoperative IOP elevations, adverse events, and early discontinuations.ResultsData were collected on 189 LASIK eyes (96 patients) and 209 PRK eyes (108 patients). Mean (standard deviation [SD]) years of age at surgery was 36.0 (11.7) and 33.9 (11.3) in LASIK and PRK patients. LE gel was prescribed most often four times daily during the first postoperative week, regardless of procedure; the most common treatment duration was 7–14 days in LASIK and ≥30 days in PRK patients. No unusual corneal findings or healing abnormalities were reported. Mean postoperative uncorrected distance visual acuity was 20/24 in LASIK and 20/30 in PRK eyes. Mild/trace corneal haze was reported in 20% of PRK patients; two PRK patients with moderate/severe corneal haze were switched to another corticosteroid. Mean postoperative IOP did not increase over time in either LASIK or PRK eyes (P≥0.331); clinically significant elevations from baseline in IOP (≥10 mmHg) were noted in only three eyes of two PRK patients.ConclusionLE gel appears to have a high level of safety and tolerability when used for the management of postoperative pain and inflammation following LASIK and PRK surgery.

Surface Ablation with 0.02% Mitomycin C for Retreatment after LASIK and LASEK

Purpose: To evaluate the efficacy and safety of surface ablation with mitomycin C (MMC) for the retreatment of refractive errors following laser-assisted in-situ keratomileusis (LASIK) and laser-assisted sub-epithelial keratectomy (LASEK). Methods: In this retrospective clinical study conducted at a single center, we evaluated 23 eyes that received surface ablation with MMC (0.02%, 20 seconds) between 2009 and 2013 for the treatment of residual refractive errors following myopic LASIK and LASEK. All eyes were evaluated for corneal thickness, initial refractive error, time interval to retreatment, amount of retreatment, duration of postoperative topical steroids use as well as uncorrected vision, spherical equivalent and corneal haziness preoperatively and 1, 3, 6 and 12 months postoperatively. Results: Initially corrected myopia in the LASIK group was -6.47 ± 2.17 D and -5.68 ± 2.51 D in the LASEK group. Mean time between initial and retreatment by surface ablation was 11.88 ± 5.59 months for LASIK and 14.07 ± 10.10 for LASEK. Retreat amount was 1.49 ± 0.36 D after LASIK and -1.65 ± 0.41 D after LASEK. At postoperative 12 months, uncorrected visions were -0.061 ± 0.886 (log MAR) in the LASIK group and -0.004 ± 0.745 (log MAR) in the LASEK group and spherical equivalents were -0.55 ± 0.56 D in the LASIK group and 0.36 ± 0.33 D in the LASEK group. Postoperative hazes developed in 1 of 8 LASIK eyes and 3 of 15 LASEK eyes which resolved with application of topical steroid for 2-3 months postoperatively. Conclusions: Surface ablation with 0.02% MMC is safe and highly effective for treating myopic regression following LASIK or LASEK. Application of 0.02% MMC for 20 seconds was effective in preventing postoperative haze formation and maintaining stable vision and spherical equivalent at 12 months after retreatment. J Korean Ophthalmol Soc 2015;56(7):992-997

Stability of Laser-Assisted In Situ Keratomileusis (LASIK) at Altitude

The U.S. Air Force approved laser-assisted in situ keratomileusis (LASIK) for aircrew in May 2007. Relative to photorefractive keratectomy (PRK), LASIK potentially offers a more rapid return to flight status; however, there are concerns regarding corneal stability at altitude after surgery. Studies have shown that hypoxia induces a myopic shift in LASIK eyes. Mountaineers treated with LASIK have similarly reported decreased distance acuity when climbing above 22,000 ft (6706 m). We evaluated visual and refractive stability after LASIK under conditions simulating an operational aviation mission. There were 24 eyes of 12 active duty subjects that were examined 1 or more months after LASIK. Measurements of high and low contrast visual acuity, keratometry, and refractive error were performed at ground level after a 2-h oxygen pre-breathe and repeated after 30 min of exposure to conditions simulating 35,000 ft (10,668 m) using a hypobaric chamber. A within subject, repeated measures t-test was used to compare findings at altitude to ground level. LASIK eyes demonstrated no clinically or statistically significant changes at altitude relative to ground level for the four parameters studied. No eyes showed more than +/-0.25 D of change on keratometry and none had a myopic shift greater than 0.25 D. LASIK eyes exposed to extreme altitudes under operational conditions, where the exposure is limited to 30 min or less, are expected to remain stable.

Astigmatism induced by conventional spherical ablation after PRK and LASIK in myopia with astigmatism &amp;lt; 1.00 D

BackgroundThe purpose of this study was to evaluate surgically-induced astigmatism after spherical ablation in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for myopia with astigmatism < 1.00 D.MethodsThe charts of patients undergoing spherical PRK or LASIK for the correction of myopia with minimal astigmatism of <1.00 D from 2002 to 2012 at the John A Moran Eye Center in Salt Lake City, UT, were retrospectively reviewed. Astigmatism was measured by manifest refraction. The final astigmatic refractive outcome at 6 months postoperatively was compared with the initial refraction by Alpins vector analysis.ResultsFor PRK, average cylinder increased from 0.39 ± 0.25 (0.00–0.75) preoperatively to 0.55 ± 0.48 (0.00–1.75) postoperatively (P = 0.014), compared with an increase in LASIK eyes from 0.40 ± 0.27 (0.00–0.75) preoperatively to 0.52 ± 0.45 (0.00–2.00) postoperatively (P = 0.041). PRK eyes experienced an absolute value change in cylinder of 0.41 ± 0.32 (0.00–1.50) and LASIK eyes experienced a change of 0.41 ± 0.31 (0.00–1.50, P = 0.955). Mean surgically-induced astigmatism was 0.59 ± 0.35 (0.00–1.70) in PRK eyes, with an increase in surgically-induced astigmatism of 0.44 D for each additional 1.00 D of preoperative cylinder; in LASIK eyes, mean surgically-induced astigmatism was 0.55 ± 0.32 (0.00–1.80, P = 0.482), with an increase in surgically-induced astigmatism of 0.29 D for each 1.00 D of preoperative cylinder.ConclusionSpherical ablation can induce substantial astigmatism even in eyes with less than one diopter of preoperative astigmatism in both PRK and LASIK. No significant difference in the magnitude of surgically-induced astigmatism was found between eyes treated with PRK and LASIK, although surgically-induced astigmatism was found to increase with greater levels of preoperative astigmatism in both PRK and LASIK.

Efficacy and Safety of Short-Duration Topical Treatment with Azithromycin Oil-Based Eyedrops in an Experimental Model of Corneal Refractive Surgery

To assess the tolerance and side effects of azithromycin eyedrops at the ocular surface after corneal refractive surgery in an experimental animal model. The effect of azithromycin eyedrops was evaluated in hen corneas that underwent laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) surgery in 1 eye, using the fellow eye (not manipulated) as a control. Animals were treated bid 3 days prior to surgery and 3 days after surgery with T1225 1.5% azithromycin eyedrops or saline eyedrops (balanced salt solution), or were left untreated as a control. Clinical course and cell biology (apoptosis, proliferation, and differentiation) measurements were assessed. Infections were present in the following proportions of corneas operated on by LASIK: 0% treated with azithromycin, 60% treated with BSS, and 30% untreated. No corneal abscess or keratitis were present in any PRK or unmanipulated corneas. Conjunctival edema and redness were less prevalent in LASIK-operated eyes treated with azithromycin than in BSS-treated or untreated eyes and were not observed in any PRK or unmanipulated corneas. In PRK-operated eyes treated with azithromycin, a decrease was observed in the apoptosis and an increase in the stromal proliferation. There were no differences in these parameters for LASIK and unmanipulated eyes. Topical administration of T1225 oil-based azithromycin eyedrops was well tolerated in both unmanipulated hen corneas and those treated with corneal refractive surgery (PRK and LASIK). T1225 demonstrated a potent antibiotic effect after LASIK treatment.

Comparison of Implantable Collamer Lens (ICL) and Laser-assisted In Situ Keratomileusis (LASIK) for Low Myopia

To compare the results of laser-assisted in situ keratomileusis (LASIK) and implantable collamer lenses (ICL) in the correction of myopia -4 to -7.88 D. A total of 1678 LASIK eyes from the Davis Duehr Eye Center, Madison, WI, and 144 ICL eyes from the 14-site US FDA Clinical Trial for ICL for Myopia were compared. Both series were concurrently operated on with 4 to 7.88 D of preoperative spherical equivalent of the manifest refraction and were examined at 1 day, 1 week, 1 month, and 6 months postoperatively. The mean baseline myopia was slightly higher in the ICL group (ICL: -6.4 +/- 1.1 D; LASIK: -5.6 +/- 1.1 D). Best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), and refractions were collected prospectively in both series. BSCVA loss of at least 2 lines was significantly higher in the LASIK series in the early healing period (1 week: 6% vs. 0.7%; P = 0.008), whereas a BSCVA gain of at least 2 lines was statistically better with the ICL at 1 (5% vs. 0.9%, P = 0.001) and 6 months (4% vs. 0.8%, P = 0.013). Proportion of cases seeing 20/15 or better uncorrected (21.6% vs. 7.8%, P < 0.001) and 20/20 or better (67% vs. 57%, P = 0.027) at 6 months postoperatively was better in the ICL group. The ICL was statistically more predictable (attempted vs. achieved) at 6 months; +/-0.50 D (79% ICL vs. 70% LASIK, P = 0.034) and +/-1.0 D (97% ICL vs. 88% LASIK, P < 0.001). Stability was achieved (95% < or = 1.0 D) at the 1-week to 1-month interval for both groups (95% LASIK; 98% ICL). The stability of refraction (< or =0.5 D change) was significantly better in the ICL group than the LASIK group through 6 months. No serious complications occurred in either series. The ICL was safer and more effective than LASIK and seems to be a viable alternative to corneal refractive excimer surgery in the treatment of low myopia.

Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia: A randomized prospective study

Objective This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). Design A randomized, prospective, multicenter clinical trial. Participants A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was −9.23 diopters (D) in the PRK group and −9.30 D in the LASIK group. Intervention All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. Main outcome measures Data on uncorrected and spectacle-corrected visual acuity, predictability, and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. Results One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity <20/40 for PRK vs. LASIK, 95% confidence interval [CI] = 0.31–1.19). After PRK, 39 eyes (57.4%) were within 1.0 D of attempted correction compared with 24 eyes (40.7%) in the LASIK group (odds ratio = 0.50 for likelihood of undercorrection 1.0 D for PRK vs. LASIK, 95% CI = 0.24–1.04); however, the standard deviation of the predictability was similar between groups: 1.01 D for PRK and 1.22 D for LASIK. From months 1 to 6, there was an average regression of 0.89 D in the PRK group and 0.55 D in the LASIK group. After PRK, eight eyes (11.8%) had a decrease in spectacle-corrected visual acuity of two Snellen lines or more; after LASIK, two eyes (3.2%) had a decrease of two lines or more (odds ratio = 3.89 for risk of loss of spectacle-corrected visual acuity for PRK vs. LASIK, 95% CI = 0.71–21.30). Only two eyes had postoperative spectacle-corrected visual acuity less than 20/32, however. Conclusions Although improvement in uncorrected visual acuity is more rapid in LASIK than in PRK, efficacy outcomes in the longer term generally are similar between the two procedures. There is a greater tendency toward undercorrection in LASIK eyes using the specific laser and nomogram in this study, but the scatter in achieved versus attempted correction is similar, suggesting little difference in the accuracy of the two procedures. A suggestion of decreased propensity for loss of spectacle-corrected visual acuity in LASIK eyes requires further investigation.

Ocular Integrity after Refractive Procedures

The purpose of the study was to determine the integrity of human eyes after refractive procedures. Whole human globes underwent either radial keratotomy (RK) with eight incisions, automated lamellar keratoplasty (ALK), photorefractive keratectomy (PRK), or excimer laser assisted in situ keratomileusis (LASIK). Eyes then were subjected to quantitatively increasing levels of trauma until rupture occurred. All eyes operated on required less energy to rupture as compared with that of control eyes. The mean number of trials required for rupture is as follows (energy doubled with each successive trial): normal, 4.29; LASIK, 3.80; ALK, 3.67; PRK, 3.60; and RK, 2.83. The level of energy required to rupture normal, ALK, PRK, and LASIK eyes was not significantly different. All RK eyes ruptured at incisions. Most ALK, PRK, and LASIK eyes ruptured near the flap edge or limbus. Most normal eyes ruptured with both corneal and scleral involvement. Age of tissue donors at the time of death and time elapsed between death and procedure were not significantly different between groups (P = 0.88 and 0.79, respectively). The energy required to rupture ALK, PRK, and LASIK eyes is not significantly different from that for normal eyes. The RK eyes ruptured with significantly less energy than did normal eyes. All RK eyes ruptured at incision sites.